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arXiv · 1204.1320

Definitive Evidence for Order-by-Quantum-Disorder in Er2Ti2O7

Lucile Savary·Kate A. Ross·Bruce D. Gaulin·Jacob P. C. Ruff·Leon Balents
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Abstract

Here we establish the systematic existence of a U(1) degeneracy of all symmetry-allowed Hamiltonians quadratic in the spins on the pyrochlore lattice, at the mean-field level. By extracting the Hamiltonian of Er2Ti2O7 from inelastic neutron scattering measurements, we then show that the U(1)-degenerate states of Er2Ti2O7 are its classical ground states, and unambiguously show that quantum fluctuations break the degeneracy in a way which is confirmed by experiment. This is the first definitive observation of order-by-disorder in any material. We provide further verifiable consequences of this phenomenon, and several additional comparisons between theory and experiment.

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Lucile Savary, Kate A. Ross, Bruce D. Gaulin, Jacob P. C. Ruff, Leon Balents. 2012-04-05. Definitive Evidence for Order-by-Quantum-Disorder in Er2Ti2O7. https://doi.org/10.1103/physrevlett.109.167201

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